Presently, in cold rolling mills, the entry strip tension of metal strip, for example steel strip, is selected in the range between 4 to 6% of the yield strength Y of the metal strip for the first pass and between 35 to 65% for subsequent passes. The exit strip tension is selected approximately between 35 to 65% of the strip yield strength Y, except for the last pass when the exit tension of the metal strip is limited to 5 to 10% of the strip yield strength Y. Under these conditions, the maximum thickness reduction of metal strip in one rolling pass is usually limited to 40-45%. Because of that, the number of rolling passes during cold rolling can be as many as five passes. Typifying these conditions is U.S. Pat. No. 5,660,070 (1997) which discloses the utilization of tension bridles in a twin stand cold rolling mill to achieve a reduction only as high as 35-40% of the total desired reduction in a single pass.
The present invention significantly overcomes the limitation of reduction of metal strip to a maximum of 40-45%. The apparatus and method of the present invention may be adapted to existing rolling mills without specially sized or configured work rolls as in U.S. Pat. No. 4,244,203 and U.S. Pat. No. 4,781,050.